After the successful Union victory during the Battle of Fort Henry on February 6, 1862, Gen. Ulysses S. Grant targeted Fort Donelson along the Cumberland River in Tennessee. After several failed counterattacks by Rebel forces, Fort Donelson surrendered, which earned Grant the nickname “Unconditional Surrender” Grant and his promotion to Major General. These two battles were the first major Union victories of the Civil War and opened the western door to the Confederacy.